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My FX4 LII engine was running very rough with loss of power and the solution.


osujason

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So my 2003 FX4 level II had started running very rough with loss of power etc, it felt like it was misfiring. Immediately went to auto zone and had them run the codes. They told me it was a small evap leak and tried to sell me a new gas cap which I declined because my gas cap looked fine. I then started inspecting the rest of the fueling system and really could not find anything obvious. I went ahead and replaced the fuel filter which likely needed replaced, but that made no difference. I then started looking at the PCV valve and discovered it was loose, it was basically just floating in the hole because the threads had broken. I purchased a new PCV valve and "glued" it securely into the hole with RTV. However, this was not the fix either, engine was still running very rough. So i took it back to Autozone and had them scan the computer again, but this time the code showing was for a misfire on cylinder 5, the small evap leak code was gone. After inspecting plugs and wires, it turns out the wire going to plug #5 was damaged so i went ahead and had new plugs and wires installed which solved the problem.

So to sum it up, I guess I had 2 issues, loose PCV valve which I suppose was causing the small evap leak code, and then the misfire on cylinder #5, I'm just not sure why the misfire code did not show up the first time when it was scanned, perhaps Autozone only read me the first code and failed to go any farther? Anyway, just figured I would put this out there in case it helps anyone.

JB
 


rubydist

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That is another reason to buy one of those inexpensive code readers and check them yourself rather than counting on the kid at the auto parts store to read them for you.
 

lil_Blue_Ford

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Glad you found and fixed the problems.

I don’t fully trust that the computers know what’s wrong sometimes. Heck, I drove my green Ranger for a few years and any time I did get a check engine light, I’d pull codes and hunt down the problem. Never got anything about an EVAP leak. Never. But when I pulled the engine and transmission for a swap, the main EVAP line going to the back came out in about 6 pieces where there’s a short section of metal. What came out had more holes than Swiss cheese. Massive EVAP leak. Computer insisted all was well. I replaced it with aluminum tube.
 

osujason

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Location
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2003
Make / Model
Ranger FX4 LvII
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Automatic
2WD / 4WD
4WD
Total Lift
stock
Total Drop
0
Tire Size
33x10.5r15 BFG KM3
That is another reason to buy one of those inexpensive code readers and check them yourself rather than counting on the kid at the auto parts store to read them for you.
You are correct. I'll be getting a code reader in the not too distant future.
 

osujason

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2003
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Ranger FX4 LvII
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Automatic
2WD / 4WD
4WD
Total Lift
stock
Total Drop
0
Tire Size
33x10.5r15 BFG KM3
Glad you found and fixed the problems.

I don’t fully trust that the computers know what’s wrong sometimes. Heck, I drove my green Ranger for a few years and any time I did get a check engine light, I’d pull codes and hunt down the problem. Never got anything about an EVAP leak. Never. But when I pulled the engine and transmission for a swap, the main EVAP line going to the back came out in about 6 pieces where there’s a short section of metal. What came out had more holes than Swiss cheese. Massive EVAP leak. Computer insisted all was well. I replaced it with aluminum tube.
Right, and I don't even know if I can trust the kid reading the codes either.
 

lil_Blue_Ford

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Right, and I don't even know if I can trust the kid reading the codes either.
Most Autozone’s have switched to a nearly idiot proof code reader. It can’t clear codes and has to be plugged into their computer in the store to read them. So less chance of employee error, but I definitely hear what you’re saying. For a long time the local Autozone would just tell me to use the end computer and they would put their password in whenever I needed it. I’d just sit there and hunt down whatever I was looking for. It was easier that way than me trying to explain why I need some random part for like a 99 Explorer for my 88 Bronco II or the like. Heck, the shocks on my choptop I have no idea what they fit stock, I just have part numbers, lol. Now I have a commercial account and the local commercial guy is great.
 

RonD

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The Bluetooth OBD2 readers are cheap, under $20 and Free APPs, uses smartphone or tablet as display

They do just fine for most users needs, read and clear codes, watch Live Data
There are $5 APPs which can get you more detailed info

Works on any 1996 and up vehicle sold in US or Canada, so not a Ford thing

I used an ELM327 for many many years no complaints, on several different vehicles

Recently(2 years ago) got a BlueDriver unit because it can also get automatic transmission codes, $100, also no complaints so far


Computer does not set a code unless the "fault" has been repeated a few times
Flashing CEL while driving indicates "hard misfires" occurring at that moment, but if you were to check the codes you probably would not see misfire codes until the next drive cycle and misfires occurred again
Computer can set "memory codes", then on the next drive cycle if that code is repeated computer will turn on the CEL
But it really depends on the code, some can reoccur and not turn on the CEL until its been repeated 3 or 4 times
Like the EVAP small leak code, that can turn on the CEL but only after computer has seen the fault several times

One drive cycle is coolant temp above 170degF then below 120degF, not related to key on and off
 
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